Abstract In accordance with RFA-DP11-005, this study will provide long-term outcome data for the prevalence, incidence and progression of radiographic knee and hip OA, knee and hip symptoms, and disability in African Americans and Whites, aged 45 years and older. It will additionally examine the occurrence and timing of concomitant obesity, diabetes mellitus, and cardiovascular disease, and their interactive effects, upon OA outcomes, and extend the timeline for examination of risk (leg length inequality) and potentially protective factors (weight maintenance) upon these outcomes. This proposal requests process and technical support to complete the 3rd follow-up (T3) of the Johnston County Osteoarthritis Project, an average of 4 - 7 years after the 2nd 5-year follow-up (T2), approximately 10 - 15 years after the 1st follow-up, and 20-25 years after the baseline examination (T0). The effect of some risk factors may take longer time periods to exert their effects than are commonly observed in most OA studies. This study with its long follow-up time is poised to fill that knowledge gap. This study of risk factors for incidence and progression of these outcomes in AAs and Whites in a rural, Southern county has included extensive radiographic, clinical, interview, and functional data on over 4,300 individuals (approximately 1/3 African American, 40% men) throughout these past 20 years. The current sample eligible for T3 includes individuals from the original T0 baseline time point as well as individuals from 2 cohort enrichments conducted in 2003-2004 and ongoing in 2011-12. The protocol and data collection instruments for T3 are now in development, and will be available and approved by the time this grant, if successful, is funded. All individuals will complete radiographic examinations of the knees, hips, patellofemoral joints, hands, and lumbar spine, physical and functional examination, extensive interviews, and DEXA, and contribute urine and blood for storage of serum, plasma, DNA and RNA. Stratified analysis and multiple logistic and polytomous logistic regression, and time-to-event analyses, with generalized estimating equations when appropriate, will be used to assess ethnic differences in the roles of risk factors assessed at T0, T1, and T2, and their timing, in the incidence and progression of the above outcomes at T3. The proposed study will thus define objectively the burden of knee and hip OA in these groups over time, increase knowledge about factors associated with the incidence and progression of OA of these joints, identify potentially modifiable risk factors for these outcomes, and identify high risk subgroups. By examining these factors in multiple aspects of the OA process in both ethnic groups within one study, efficiency and significant impact upon the public health can be maximized.